The Greenburgh Police Department is warning about a rise in car thefts in the city, with the thieves targeting luxury vehicles with high-tech electronic keys left inside.

Neighboring areas such as Dobbs Ferry and Irvington had seven cars stolen in the past month, and Greenburgh Police Chief Joseph DeCarlo says the thieves are banking on keyless entry, which can make the vehicles easier to steal.

"Perpetrators can come close to cars and be able to detect which cars have these keyless devices left in their car," he says.

Julian Brown, of Yonkers, says he made the mistake once of leaving his electronic key inside his car. Luckily, his Porsche was never stolen, but he says he'll never do it again.

Authorities say the best way car owners can protect themselves is to lock up the car and take the key with them.